An inkjet printing system, as one embodiment of a fluid ejection system, may include a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead, as one embodiment of a fluid ejection device, ejects drops of ink through a plurality of nozzles or orifices and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more columns or arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
The droplets themselves, as ejected from the printhead, can affect print quality of the printed image. This is because an ejected drop may not always be a single round (spherical) drop. For example, the ejected drop may include a tail which breaks off during ejection and forms smaller drops separated from the main drop. These smaller drops, if sufficiently small and detached from the main drop, may land adjacent to the main drop on the media and cause spray, namely irregularities, change in optical density depending on the direction of printing (e.g., left-to-right vs. right-to-left), loss of contrast, and/or loss of sharpness depending on their size, number, and/or distance from the main drop. This spray, therefore, may degrade print quality.
In addition, drop ejection frequency can also cause spray and edge raggedness. At high frequencies where firing chamber design may be unable to sufficiently replenish the lost volume of an ejected drop, the firing chamber may only partially fill thereby resulting in drops of smaller drop volume. Conversely, the firing chamber may overfill by a small amount after the first and subsequent drop ejection thereby resulting in drops of larger drop volume. As such, depending on the mass of the drop, the shapes of the drops may vary and have unintended trajectories. These unintended trajectories may cause the odd shaped drop to land ahead of the previous drop and cause edge raggedness, or break into smaller drops and cause spray. This again may degrade print quality. Edge raggedness can also be caused by ink wicking on the media which may be a function of the ink properties.
For these and other reasons, a need exists for the present invention.